This document is entitled: “Common Pitfalls Regarding Necklines.” At the bottom (cut off) it reads: These pages have been viewed by Rabbi Nissim Karelitz Shlit”a and Rabbi Moshe Shaul Klein Shlit”a from the rabbinic court of Rabbi Vozner Shlit”a.*
You can see common Israeli neckline styles here. The rabbis who signed off on the above document hold by stringencies not observed by all camps in the Orthodox community. Rabbis from the national religious community are more lenient about how much to expose, but none would permit a plunging necking or decolletage.
Of the 22 pictures, the first twelve are labelled “Not Kosher”:
1-3, 5: The neckhole is too open.
4: The neckhole needs to be above the necklace at the sides. [To judge the neckline, a woman wears a chain around her neck. The back and sides of the collar or outfit must cover her skin to the point just above where the chain lies on her neck. As pictured, a boat neckline exposes too much.]
6: The wide neckhole is not covered by the scarf, according to Jewish law.
7: From the back. The opening must be closed with a zipper.
8: A safety pin should be added to the top button, which does not cover according to law.
9-10: The shoulder bag pulls the collar and exposes the shoulder.
11: The neck is covered in front according to law, but not the sides.
12: The dickey (libit) is too low and does not cover properly.
Thirteen through eighteen, inside the central hexagon, are kosher:
13: The dickey (libit) covers according to Jewish law.
14: Closed according to Jewish law.
15: The neck opening is slightly higher than the chain.
16-18: The neckline is closed according to Jewish law.
Nineteen through twenty-two are pictures of views from the back (hard to tell when there are no faces visible).
19: Not kosher, the neckhole is too open.
20: Kosher, the neckhole covers according to Jewish law.
21: Not kosher, the neckhole is under the chain.
22: Kosher, the neckhole is above the chain.
Please keep comments respectful.
*Shlit”a: An acronym meaning “May he live a good and long life.”
Update: G6 left the following comment:
The document you posted is certainly the strictest stance and many very frum, yeshivish, right wing rabbonim would NOT agree that all these stringencies are required.
I would suggest that everyone consult their own posek (rabbinic authority) instead of imposing (possibly unnecessary) restrictions upon themselves based on an internet posting.
G6, there are people who are looking for more stringencies, but this is not the strictest opinion. I have seen sources quoted for covering the neck entirely.